The present invention relates to a method of forming a contact hole of a semiconductor device and, more particularly, to a method of forming a contact hole having a micro pattern size.
In general, a semiconductor device consists of a number of unit elements. As a semiconductor device is highly integrated, semiconductor elements must be formed on a predetermined cell area with a high density. Due to this, the size of a unit element, such as a transistor or a capacitor, gradually decreases. In particular, in semiconductor memory devices such as Dynamic Random Access Memory (DRAM), the size of semiconductor elements formed within a cell is decreased as the design rule is reduced. In recent years, a minimum line width of a semiconductor DRAM device is 0.1 nm or less and even requires 60 nm or less. Thus, many difficulties occur in a manufacturing process of semiconductor elements constituting a cell.
In semiconductor devices having a line width of 60 nm or less, if a photolithography process is performed using ArF exposure having a wavelength of 193 nm, additional requirements, such as prohibition of deformation of a photoresist, which occurs during etching, are necessary in the existing etch process concepts (formation of an accurate pattern, a vertical etch profile, and so on). Accordingly, upon fabrication of semiconductor devices of 60 nm or less, it has became an important subject to develop a process condition for fulfilling the existing requirements and new requirements, such as prevention of pattern deformation, at the same time from a viewpoint of etching.
The conventional method for forming a micro contact hole of 100 nm or less, which exceeds the limit resolutions of exposure equipment, includes a method of forming a photoresist pattern for a contact hole and then heating the pattern over a glass transition temperature of a photoresist material in order to form a contact hole pattern having a size smaller than an original pattern size through flow, a method of reducing the size of a contact hole using a process employing Resist Enhancement Lithography Assisted by Chemical Shrink (RELACS) material, and so on.
In addition to the above methods, there is a need for a method for forming a micro contact hole exceeding the limit resolutions of exposure equipment.